thanks in advance...

i have a 1998 dodge ram 1500 quad cab with 5.9L. 125k miles (running rough for last couple of days). day 1 i had p0305, so i replaced #5 plug, #5 wire and #5 injector (no help). day 2 i replaced all wires, plugs, cap, rotor, cleaned throttle body and replaced iac... i reset computer with scan tool (running better, but still slight miss at idle). day 3 starts hard when cold, idles rough... now getting p0300, p0304 and p0305. Please note: the cat is 2-3 years old.

i have done the following:
replaced cap (terrible condition after two years)
rotor (ok)
plugs
wires
removed and cleaned throttle body (replaced gasket)
replaced iac
replaced #5 injector

how do i ohm out the coil and crank sensor? what should readings for normal be? any other suggestions? THANK YOU- Dave

 

i'd recommend a compression test or leak down test to check for major problems that are unmentionable....

 

ooooh, the unmentionables. Hopefully not.

You say running rough. Does the roughness have a rhythm to it OR do you feel a random misfire?

 

I know that you said that the cat is only 2 or 3 yrs old, but.... those are the same codes I was getting on my '98. I did same as you, wires, plugs, cap, iac, speed sensor, and mass air flow. Did you check your routing of the plug wires? There is a TSB out about plug wire routing. In the end it wound up being the cat was bad. Take it to a Midas and let them pressure test it for you, then you will know for sure (It is also FREE). lso, when you cleaned the TB, did you look down in the plenum to see if there is oil leaking into it. Mine was leaking oil and that is what ruined the CAT. Replaced the plenum pan and gaskets. Put on a new CAT, and have not had any problems since. Dumped a lot of $$ on O2 sensors and various other sensors, when they were not the problem!

 

Why would Midas pressure test it for free?

 

compression test:
1-150
2-160
3-160
4-30
5-0
6-150
7-160
8-160

i opened up the pass side and visually inspected valve train... looks and functions normally. guess I'm ready for a couple of long nights... anyone have a 5.9L ready to go in northern california?

 

damn. the unmentionables.

zero? i've never seen a zero before.
and 4 and 5 are on opposite sides. any chance of malfunction of the test?
do you think one cylinder has been out for awhile, and now you've lost a second one.
it just seems really odd to me that opposite banks would go out at the same time.
i would have suspected adjoining cylinders.

um, you haven't been doing something naughty have you ? maybe a little NOS ?

 

zero = hole in piston or missing valve

dude, that sucks.

 

Did he get n a shootout in his truck?

 

No...no nos.

Heads are off- #5 exhaust valve is worn at seat (daylight shinning through). #4 looks ok (probably worn as well). Hoping to get back together tomorrow. Thanks for all your help.